In recent years, an inner surface progressive multi-focal lens having a progressive face on the concave surface side (inner surface side) of a spectacle lens has been developed. The inner surface progressive multi-focal lens can reduce the image jump and the distortion which are defects of a progressive multi-focal lens which has a progressive face on the convex surface side thereof, and can raise the optical performance remarkably.
Polishing of a spectacle lens for generating an optical surface in the form of a concave surface of such an inner surface progressive multi-focal lens as described above forms the concave surface of the working object lens into a predetermined optical surface through cutting, grinding, mirror polishing and so forth. Such a numerically controlled machining apparatus as shown in FIG. 10 has been developed as a polishing apparatus which can cut the concave surface of a spectacle lens.
Processing data for numerical control calculated by a computer for calculation based on prescription data for a spectacle lens inputted from an inputting apparatus is transmitted to the numerically controlled machining apparatus 600 through a host computer and stored into an internal storage apparatus of the numerically controlled machining apparatus 600.
The numerically controlled machining apparatus 600 includes an X-axis positioning mechanism 610 and a Y-axis positioning mechanism 620 on a bed 601. The X-axis positioning mechanism 610 is driven to move in a substantially horizontal X-axis direction by an X-axis driving motor and an encoder 611. The position of the X-axis positioning mechanism 610 in the X-axis direction is indexed by the encoder 611. A work shaft rotating mechanism 612 is secured on the X-axis positioning mechanism 610 and has an axis of rotation coincident with a substantially horizontal Y-axis direction perpendicular to the X axis. A chuck 613 is attached to the work shaft rotating mechanism 612 and driven to rotate by a work rotary shaft driving motor and an encoder 614. The rotational position of the chuck 613 is indexed by the encoder 614. A working object lens (work) 10 is attached to the chuck 613 through a block jig. The Y-axis positioning mechanism 620 is driven to move in the Y-axis direction by a Y-axis driving motor and an encoder 621. The position of the Y-axis positioning mechanism 620 in the Y-axis direction is indexed by the encoder 621. Two cutting tool holders including a first cutting tool rest 622 and a second cutting tool rest 623 are secured on the Y-axis positioning mechanism 620, and a roughing cutting tool 624 is secured to the first cutting tool rest 622 while a finishing cutting tool 625 is secured to the second cutting tool rest 623.
According to a controlling method, the center coordinates of a tip end of the cutting tool 624 or 625 are positioned in a normal direction to a working point of the work 10 using the three axes of the X-axis positioning mechanism 610, Y-axis positioning mechanism 620 and work shaft rotating mechanism 612. Then, the positioning of the center coordinates of the tip end of the cutting tool corresponding to the working point is performed continuously to perform shape generation based on a lens design shape. At this time, the work 10 is rotated at a speed within 100 to 6000 rpm depending upon the shape of the work and the type of working between roughing and finishing by the work shaft rotating mechanism 612. The rotational position of the work 10 is indexed by the encoder 614, and the Y-axis positioning mechanism 620 and the X-axis positioning mechanism 610 are positioned in synchronism with the rotation of the work 10. In particular, while the work 10 is rotated, the relative positions between the cutting tools 624 and 625 and the work 10 in the direction of the Y axis coincident with the axis of rotation of the works 10 and the relative positions between the cutting tools 624 and 625 and the work 10 in the X-axis direction are synchronized with the rotation of the work 10.
The numerically controlled machining apparatus 600 changes over between the roughing cutting tool 624 and the finishing cutting tool 625 to perform a shaving process.
The numerically controlled machining apparatus 600 having such a configuration as described above can generate any surface shape and can perform shape generation of an inner surface progressive multi-focal lens.
Conventionally, such a block jig as shown in FIG. 11 is used as the block jig for mounting the working object lens 10 on the chuck 613 of the numerically controlled machining apparatus 600.
The block jig 400 shown includes a mounting portion 410 for mounting the block jig 400 on the chuck 613 of the machining apparatus 600, and a low melting point metal portion 420 for coupling the mounting portion 410 and the working object lens 10 to each other. The low melting point metal portion 420 is formed using a ring-shaped jig not shown as a mold by interposing the ring-shaped jig between the mounting portion 410 and the working object lens 10, filling molten metal having a low melting point into a gap of the ring-shaped jig, leaving the low melting point metal to be solidified and then removing the ring-shaped jig.
However, such a block jig 400 as described above is not necessarily suitable for the numerically controlled machining apparatus 600 because a block jig which has been used in a conventional polishing apparatus which uses rubbing is used as it is as the block jig 400 in the numerically controlled machining apparatus 600.
For example, when the mounting portion 410 is mounted and set in position on the chuck 613 of the numerically controlled machining apparatus 600, the reference for machining is provided by the angularity of a corner portion 430 at which the mounting portion 410 intersects with the low melting point metal portion 420 which uses a ring-shaped jig as a mold. However, a gap or the like appears between the mounting portion 410 and the low melting point metal portion 420 due to appearance of a cavity in or shrinkage of the low melting point metal portion 420. Therefore, the block jig 400 has a problem in that the angularity of the corner portion 430 cannot readily be formed accurately and numerically controlled mashing of a high degree of accuracy is difficult.
On the other hand, where the numerically controlled machining apparatus 600 is used, it is possible to automatically perform a series of processes of incorporating a conveying apparatus, carrying in and mounting a polishing jig having a working object lens held thereon on the chuck, performing polishing of the working object lens and then carrying out the polishing jig with the worked lens held thereon.
However, the conventional block jig 400 is not ready for such automatic conveyance.
Therefore, it is demanded to develop a novel polishing jig suitable for the numerically controlled machining apparatus 600 which performs shape generation of the concave surface of an inner surface progressive multi-focal lens.
Also a conveyor tray for exclusive use is required which can accommodate and protect such a polishing jig as just described with a working object lens held thereon and is ready for automation of a numerically controlled machining apparatus.
A numerically controlled machining apparatus can perform fully automatic polishing if a step of conveying a polishing jig with a working object lens held thereon to a polishing apparatus, another step of conveying the polishing jig with the worked lens held thereon to a next step and other necessary steps can be automated.
However, polishing of a spectacle lens involves special conditions. For example, usually a pair of left and right spectacle lenses are worked together. Also after polishing, it is demanded that a pair of left and right spectacle lenses be fed through a dyeing step, an inspection step, a packing step and so forth. Therefore, it is demanded to use a conveyor tray which accommodates a pair of left and right lenses. Besides, it is demanded that, upon polishing of a pair of left and right lenses, they may not be brought out of the paired relationship.
Further, in polishing of a lens by the numerically controlled machining apparatus 600, several minutes are required for working of one lens. Therefore, a one-by-one successive working method wherein working object lenses are taken out one by one from a conveyor tray and worked and a lens whose working is completed is conveyed back to its original position of the conveyor tray, whereafter another working object lens is conveyed into the polishing apparatus has a problem in that the efficiency is low.
The present invention has been made in view of such circumstances as described above, and it is a first object of the present invention to provide a polishing jig suitable for a numerically controlled machining apparatus.
It is a second object of the present invention to provide a conveyor tray for exclusive use for conveying a polishing jig of the type described.
It is a third object of the present invention to provide a conveying method wherein working object articles can be worked efficiently by a working apparatus which requires a long period of time for working while they are kept accommodated in pair in a conveyor tray of the type described.
It is a fourth object of the present invention to provide a conveying apparatus which can implement a conveying method of the type described.